Title

Author

Date of Award

2010

Document Type

Campus Access Dissertation

Department

Exercise Science

First Advisor

Steven Blair

Abstract

This dissertation project describes the Aerobics Center Longitudinal Study (ACLS) women and men's association between adiposity and the development of hypertension and Lifestyle Education for Activity and Nutrition (LEAN) Study primary outcomes with the SenseWearTM Armband.

The ACLS was used for studies 1 and 2 in this dissertation project. General obesity is a major risk factor for the development of hypertension (HTN). However, it is not well-studied whether central obesity and fat distribution are also related to the future HTN. 13,897men and 5,296 women healthy normotensive aged 20-100 years completed a baseline examination during 1976-2004 and were followed for HTN incidence. Incident HTN was identified via follow-up mail-back surveys. Obesity was defined as Body mass index (BMI) ≥ 30 kg/m2, waist circumference (WC) ≥ 102 cm, or percent body fat ≥ 25%. In a subgroup of women (n = 3,189) with complete data on all the five adiposity measures, significant positive associations with HTN were seen across incremental fifths of BMI, percent body fat, and FM (P trend < 0.05 each), but not WC and FFM. In men, adiposity factors were grouped based on the clinical outpoints, HTN incidence risk was significantly higher in BMI-defined overweight (HR, 1.53; 95% CI, 1.38-1.70) and obese (HR, 2.15; 95% CI, 1.83-2.53) compared with normal weight men; in WC-defined abdominal obese (HR, 1.57; 95% CI, 1.38-1.79) compared with normal WC men; in percent body fat-defined obese (HR, 1.47; 95% CI, 1.31-1.64) compared with normal percent body fat men, respectively. In summary, BMI, WC, and higher percent body fat are all significant risk factors for the development of incident hypertension. By using all 3 measurements, we can improve risk stratification; but this may not always be practical.

The purpose of the LEAN randomized controlled trial is 1) to assess a real-time self-monitoring strategy for physical activity and diet in conjunction with GWL to promote weight loss and waist circumference reduction compared to a standard care intervention and to a standard GWL without real-time monitoring, and 2) to assess weight loss and waist circumference reduction when using real-time self-monitoring alone. Lastly, our primary goal was to investigate the independent and joint associations between BMI, WC, and percent body fat and incident HTN in a cohort of normotensive, healthy men and women from the ACLS.

The SenseWearTM Armband is a physical activity monitor developed to improve lifestyle and weight management. In using this device individuals obtain real-time feedback on energy expenditure and energy intake, which provides an estimate of energy balance. To our knowledge, no studies have evaluated whether weight loss can be promoted in overweight and obese adults through a lifestyle intervention based on the armband. We recruited 197 sedentary overweight or obese adults (age, 46.8 ± 10.8 y; BMI, 33.3 ± 5.2 kg/m2; 81% women, 32% African-American) from the greater Columbia, South Carolina area. Participants were randomized into 1 of 4 groups that received a self-directed weight loss program via an evidence-based weight loss manual (Standard Care, n=50), a group-based behavioral weight loss program (GWL, n=49), the armband alone (SWA-alone, n=49), or the GWL plus the armband (GWL+SWA, n=49) during the 9 month intervention. All participants received the weight loss manual at baseline. Participants in the group-based programs (GWL and GWL+SWA) received 14-15 one-hour group counseling sessions over the first 4 months and 6 telephone counseling sessions during the last 5 months. Participants wearing the armband (SWA and GWL+SWA) wore the monitor daily and recorded energy intake regularly using the SenseWearTM software. Participants completed the study in three different waves. The primary outcome was body weight and waist circumference. A mixed-model repeated-measures analysis compared change in the intervention groups to the control group on weight status after adjusting for age, sex, race, education, and recruitment wave. Seventy percent of participants had body weight assessed 4 months after randomization (58% of control and 72% of intervention participants). Sixty-two percent of the participants completed the month 9 assessment (52% control and 70% intervention). After controlling for age, gender, race, education, and wave there was significant weight loss in all 3 intervention groups (GWL, 1.86 kg , P=0.05; SWA-alone, 3.59 kg, P<0.01; GWL+SWA, 6.58 kg, P<0.0001) but not in the Standard Care group (0.91 kg, P>0.05). Only the GWL+SWA group achieved significant weight loss compared to the Standard Care group (P=0.02). Significant waist circumference reductions were achieved in all 4 groups (Standard Care, 3.53 cm, P=0.0003; GWL, 2.42 cm, P=0.007; SWA-alone, 3.54 cm, P<0.01; GWL+SWA, 6.77 cm, P<0.0001), but no group had significantly reduced waist circumference compared to the Standard Care group. The armband may be a useful tool to enhance lifestyle changes that promote weight loss in sedentary overweight or obese adults. For optimal weight loss results the use of the armband and group-based behavioral intervention may be needed.

This proposed work addressed three issues: (1) the effects of the independent and joint associations of BMI, waist circumference, and percent body fat on incident hypertension of nomotensive women, (2) the effects of the independent and joint associations of BMI, waist circumference, and percent body fat on incident hypertension of nomotensive men, and (3) the effects of the use of wearable technology (SenseWearTM Armband) on weight loss and waist circumference in sedentary, overweight individuals. The future trend in health care and the research setting seems clear, using lifestyle interventions to prevent and treat chronic diseases. User friendly devices that provide both the individual and research/health care providers with objective information about the wearer's lifestyle offer many possibilities to improve the treatment and management of diseases, including obesity. Furthermore, diet and physical activity are lifestyle and behavioral factors that play a major role in the etiology and prevention of many chronic diseases, such as hypertension and obesity as well as in maintaining weight loss throughout the lifespan.